mybatis learning notes, 2.MyBatisTest

1. Introduction

1. Interface programming

• Native: Dao = = = = > daoimpl
• mybatis: Mapper ====> xxMapper.xml

2. SqlSession represents a session with the database; It must be closed after use;

3. SqlSession, like connection, is non thread safe. You should get a new object every time you use it.

4. The mapper interface does not implement classes, but mybatis will generate a proxy object for this interface. (bind interface to xml)

EmployeeMapper empMapper =	sqlSession.getMapper(EmployeeMapper.class);

5. Two important profiles:

• Global configuration file of mybatis: contains database connection pool information, transaction manager information, etc... system operation environment information
• sql mapping file: saves the mapping information of each sql statement: extract the sql.

2. Get SqlSessionFactory

public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}

• 1. Create a SqlSessionFactory object according to the xml configuration file (global configuration file), which has some running environment information of the data source
• 2. sql mapping file; Configure each sql and sql encapsulation rules.
• 3. Register the sql mapping file in the global configuration file
• 4. Write code:
  • 1) . obtain SqlSessionFactory according to the global configuration file;
  • 2) . use the sqlSession factory to obtain the sqlSession object and use it to perform addition, deletion, modification and query. An sqlSession represents a session with the database and is closed after use
  • 3) . use the unique flag of sql to tell MyBatis which sql to execute. sql is saved in the sql mapping file.

3. Test test01() directly implements the SqlSession object

1. Get sqlSessionFactory object
   SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
2. Get SqlSession object according to sqlSessionFactory
   SqlSession openSession = sqlSessionFactory.openSession();
3. Implement sql query according to SqlSession. Method (method, parameter).
   openSession.selectOne("mybatis.dao.EmployeeMapper.getEmpById", 3);

@Test
public void test() throws IOException {
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			Employee employee = openSession.selectOne(
					"mybatis.dao.EmployeeMapper.getEmpById", 3);

			System.out.println(employee);
		} finally {
			openSession.close();
		}

	}

Get the sqlSession instance and directly execute the mapped sql statements
Unique identifier of sql: statement Unique identifier matching the statement to use
parameter A parameter object to pass to the statement

4. Test test02() to obtain the implementation class object of the interface getMapper

1. Get sqlSessionFactory object
   SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

2. Get SqlSession object according to sqlSessionFactory
   SqlSession openSession = sqlSessionFactory.openSession();

3. Gets the implementation class object of the interface
   A proxy object will be automatically created for the interface, and the proxy object will execute the addition, deletion, modification and query methods

   EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
   Employee employee = mapper.getEmpById(2);

@Test
public void test02() throws IOException {
		// 1. Get sqlSessionFactory object
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		// 2. Get sqlSession object
		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			// 3. Gets the implementation class object of the interface
			//A proxy object will be automatically created for the interface, and the proxy object will execute the addition, deletion, modification and query methods
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			Employee employee = mapper.getEmpById(2);
			System.out.println(mapper.getClass());
			System.out.println(employee);
		} finally {
			openSession.close();
		}

	}